1. Technical Field
The present disclosure relates to a sensor module, a kit and a method for determining a concentration of at least one analyte in a body fluid of a user. The devices and methods according to the disclosed embodiments may mainly be used for long-term monitoring of an analyte concentration in a body fluid, such as for long-term monitoring of a blood glucose level or of the concentration of one or more other types of analytes in a body fluid. The disclosed embodiments may be applied both, in the field of home care, as well as in the field of professional care, such as in hospitals. Other applications are also feasible.
2. Description of the Related Art
Monitoring certain bodily functions, more particularly monitoring one or more concentrations of certain analytes, plays an important role in the prevention and treatment of various diseases.
In addition to so-called spot measurements, in which a sample of a bodily fluid is taken from a user in a targeted fashion and examined with respect to the analyte concentration, continuous measurements are increasingly becoming established. Thus, in the recent past, continuous measuring of glucose in the interstitial tissue (also referred to as continuous monitoring, CM), for example, has been established as another important method for managing, monitoring and controlling a diabetes state.
In the process, the active sensor region is applied directly to the measurement site, which is generally arranged in the interstitial tissue, and, for example, converts glucose into electrical charge by using an enzyme (e.g. glucose oxidase, GOD), which charge is related to the glucose concentration and can be used as a measurement variable. Examples of such transcutaneous measurement systems are described in U.S. Pat. No. 6,360,888 B1 and in US 2008/0242962 A1.
Hence, current continuous monitoring systems are generally transcutaneous systems. This means that the actual sensor or at least a measuring portion of the sensor is arranged under the skin of the user. However, an evaluation and control part of the system (also referred to as a patch) is generally situated outside of the body of the user, that is to say outside of the human or animal body. In the process, the sensor is generally applied using an insertion instrument, which is likewise described in U.S. Pat. No. 6,360,888 B1 in an exemplary fashion. Other types of insertion instruments are also known.
WO 2008/124597 A1 discloses an analyte sensing device having one or more sensing electrodes. The analyte sensing device comprises a main body configured to reside on the skin of an individual when in use, the main body having one or more electrical components. The analyte sensing device further comprises an analyte sensing electrode extending substantially perpendicularly from and electrically coupled to the main body. The analyte sensing electrode is configured for insertion into the skin of the individual.
Transcutaneous sensor systems typically imply a large number of technical challenges. Thus, a first challenge resides in the fact that the lifetime of a sensor is limited. A sensor is generally worn for approximately one week. After that, influences such as enzymes being used up and/or a sealing off in the body generally reduce the sensitivity of the sensor, or it is expected that the sensor fails. Increasing the duration of wear is an area of current research. However, this means that the sensor and, optionally, components directly connected to the former such as an insertion needle, are often designed as replaceable components. Accordingly, the sensor and optionally further replaceable components generally constitute a so-called disposable. By contrast, in many cases, the evaluation and control part of the system is reused. Accordingly, this evaluation and control part is often embodied as a so-called reusable.
The separation between a disposable and a reusable, however, generally implies additional technical challenges. Thus, a significant challenge resides in the fact that the sensitive interface between the disposable part and the reusable part is susceptible to contamination, which might lead to deterioration of the quality of the electrical measurements. Further, electrochemical systems typically are based on a potentiostatic measurement principle and, generally, may sustain very small electrical currents only, since, with larger electrical currents, electrode deterioration may occur. The deterioration of measurement signals may occur gradually, over a long time period and may be detected electronically only with a large technical effort. These technical challenges are increased by the fact that the reusable part is generally handled by the end-user or patient rather than by trained medical staff.
A further challenge of continuous monitoring systems resides in the fact that these systems require a constant effort to keep the volume of the sensor system or at least the part of the sensor system worn on the user's body at a low level, in order to increase the comfort of wearing. Thus, the functionality of the sensor system generally has to be kept at a low level, in order to avoid voluminous components such as displays or user interfaces. This reduction of functionality, however, often leads to the fact that remote resources have to be used, such as for data evaluation and/or communication with the user. In this case, however, unidirectional or bidirectional exchange of data and information between the sensor and the remote device becomes an issue. Several systems for managing this communication are known in the art.
WO 2012/068393 A1, US 2010/0324392 A1, WO 2012/007437 A1, WO 2011/154372 A1, WO 03/005891 A1, U.S. Pat. No. 8,280,476 B2, EP 1 611 838 B1, WO 2008/083379 A1, EP 1 850 226 A1, US 2005/0199494 A1, and US 2009/0240128 A1 disclose various concepts for analyte monitoring systems, including concepts for a modular setup of the systems and various concepts for data transmission of measuring data.
A further challenge in many concepts for continuous monitoring of one or more analytes resides in an energy supply of the various components of the systems. In U.S. Pat. No. 7,756,561 B2, a method and an apparatus for providing a disposable power supply source integrated into the housing of the transmitter unit mount that is placed on the skin of the patient and configured to receive the transmitter unit are disclosed. The transmitter unit mount is configured to be disposable with the analyte sensor so that power supply providing power to the transmitter unit is also replaced. The transmitter unit may include a rechargeable battery that is recharged by the power supply unit of the transmitter unit mount when the transmitter is mounted to the transmitter unit mount. A similar concept is disclosed in US 2009/0171178 A1.
In WO 2010/091028 A1, methods and devices to monitor an analyte in a body fluid are provided. Therein, an on-body patch device is used which may communicate with a reader device via RF. Inter alia, it is disclosed that the reader device may be configured to provide RF power to the on-body patch device. In response, the on-body patch device may be configured to generate an output signal, e.g. an RF signal, and transmit it to the reader device which includes, among others, data indicating the glucose measurement.
Still, despite the progress that has been made with the above-mentioned concepts, some major technical problems and challenges remain. Thus, still, functionality and energy concepts of the sensor systems will have to be improved, in order to increase usability of insurgent sensors and to improve the user's comfort by reducing the frequency of replacing the insurgent sensor. Since, with improved sensor chemicals, the actual sensor lifetime steadily increases, there remains a demand for improved energy concepts for long-term analyte monitoring systems.